The present invention concerns an object having a rosy pink colored covering on a substrat forming the body of the object, said covering comprising a first layer of nitride of an element chosen from the group comprising Ti, Zr, Hf, or a mixture of these elements, said first layer including at least an element chosen amongst Al, C and elements of the groups Vb and VIb.
A rosy pink colored covering has already been proposed in a single layer of nitride as defined above. In this regard, reference may be made to the document published in February 1991 by the-company Leybold AG (Germany) and titled: "What you ever wanted to know about deco coatings", Part III. A chapter of this publication is concerned with obtaining of the coloring called "rosy pink", this being a pink which has reddish tones and which is currently fashionable for covering the mountings of spectacles. Until now such a covering which is sufficiently hard so as to be resistant against wear and scratches has not been proposed, the alloys which have been proposed being relatively soft and comprising for example intermetalic compositions including essentially palladium and indium, the color of this composition varying from pale-yellow to the color gold or rose-gold. Such a composition, the hardness of which is hardly greater than 350 HV.sub.1, is described in U.S. Pat. No. 4,804,517.
A color may be characterised by its shade, its clarity and its saturation. Apparatus, for example the colormeter Minolta CR200 and the spectrophotometer Perkin-Elmer 555 equipped with an integration sphere, convert all the colors within the range of human perception into a digital code which allows several people to express very accurately the color under discussion. This code is defined in a recommandation of the International Lighting Committee (CIE, 1976). This system espresses the color L* a* b*. When a color is expressed in this system, the clarity (luminance) is indicated by the value L* whilst the,shade and the saturation are expressed by a* and b*; a* and b* indicate two axes of color, i.e. a* the red-green axis and b* the yellow-blue axis. The positive values of a* correspond to red, negative to green, whilst the positive values of b* correspond to yellow and negative to blue. The value of the clarity (luminance) L* may vary between 0 (black) to 100 (white)
The publication of the Leybold company mentionned above defines the coloration "rosy pink" by the following values: L*=73, a*=8 and b* =5. In order to achieve this coloration, several compositions have been proposed which are all a hard layer (&gt;600 HV1) of nitride applied to a substrate by physical vapor deposition (PVD), each of these layers only slightly approaching the definition of color indicated for rosy pink. These compositions are given hereafter with the corresponding coloration.
______________________________________ Ti.sub.90 Al.sub.10 N.sub.x L* = 57, a* = 9, b* = 5 Ti.sub.95 Al.sub.5 N.sub.x L* = 57, a* = 10, b* = 8 Ti.sub.80 Al.sub.10 V.sub.10 N.sub.x L* = 60, a* = 7, b* = 7 Zr.sub.80 Al.sub.20 N.sub.x L* = 53, a* = 6, b* = 6 Ti.sub.80 Cr.sub.20 N.sub.x L* = 63, a* = 4, b* = 9 TiCxNy L* = 61, a* = 7, b* = 5 ______________________________________